During WWIIMandatory Palestine twice faced the danger of invasion by the German army and its allies. The first began when Nazi Germany conquered France in June 1940 and the rise of the pro-Nazi regime of Vichy France, which controlled Lebanon and Syria. This made the possibility of a German invasion from the north highly probable. That summer the British armed forces started preparing a defense line against invasions from the north.

The following year, between June–July 1941, the British conquered Lebanon and Syria against Vichy France. However, this had not removed the threat of a major German invasion from the north, as the British believed that the Red Army might not hold the line against Nazi Germany. Even though the defense line in Russia had been stabilized, the British made a strategic plan for the retreating troops out of Syria to be assembled in the mountainous region between Mount Carmel and the Jordan Rift Valley. This topography was believed to be effective against the Nazi German tank force (Panzerwaffe). This plan was referred to as Palestine Final Fortress or in short PFF. In the winter of 1942 massive infrastructure work began and the whole Mount Carmel region was declared as a closed military area.

In the following years the weight of the war moved towards North Africa, and a new threat of a German invasion from the South arose. The Yishuv leaders suggested the idea of using the already built defense infrastructures as a final stronghold of the Jewish population in case Germany invaded Palestine. Although there was some public panic (200 days of dread), no further actions were taken by the British nor by the Yishuv to prepare against the scenario of invasion from the South.